Apparatuses for producing foam-in-bag cushions for use as packaging materials are generally known in the art. Such cushions are typically comprised of opposing sheets of plastic film having their edges sealed and being filled with a foam-forming material. The cushions are inserted into the packaging box immediately after their production where the foam is allowed to expand and harden, taking on the shape of the packaging container and the material being packaged.
Multiple patents exist describing such cushions as well as apparatuses and methods for their production. For example, U.S. Pat. No. 6,131,375 discloses an apparatus for successively forming foam cushions from two reactive foam components that, when mixed together, form an expandable foam, and from two opposing flexible panels that enclose the expandable foam. The apparatus advances two opposing film panels across a foam dispensing assembly so that the two panels are on opposite sides of the foam dispensing assembly, which separately dispenses the two reactive foam components into the space between the film panels where the components mix to form the foam. The marginal edges of the film panels are sealed, creating a foam-filled bag.
As the foam-forming composition used to fill the cushions reacts within the cushions, the reaction generates gases, such as carbon dioxide and water vapor, which lead to expansion of the foam and complete filling of the bag. Furthermore, air is drawn into the bag aiding in the expansion of the foam. It is therefore necessary to provide ventilation for the bag to allow the expanding gases to escape, and to allow air to be drawn into the bag. Without ventilation, the bag could be ruptured by the expanding foam. Additionally, lack of ventilation can lead to collapse of the foam or incomplete formation of the foam. Previous methods have been proposed for providing ventilation. According to U.S. Pat. No. 5,679,208, an apparatus is provided for forming a bag wherein the side seals do not extend the full length of the side, thus leaving vent openings in the sides. An alternate method for providing ventilation entails creating small slits in the bag using knives or heated wires.
Slit-formation is a method for providing ventilation that is presently used with the SpeedyPacker™ foam-in-bag packaging system available from Sealed Air Corporation (Saddle Brook, N.J.). While ventilation using slit-forming mechanisms is effective at allowing formed gases to escape, the slits have the disadvantage of being large enough in size to allow foam to escape the bag, especially with small size applications, such as continuous foam tubes (CFTs). This is problematic in that the cushions are generally placed in contact with the material to be packaged to allow the cushion to take on the shape of the packaged material. It is undesirable to allow foam escaping the bag to make contact with the packaged materials.
It has been proposed that the problems associated with using slit vents can be alleviated through the use of needle rollers to create an area of pinhole vents in the foam-filled bags. Needle rollers have been used with foam-in-bag cushion producing apparatuses, such as the SpeedyPacker™ system, and have been shown to be effective at providing ventilation while preventing the escape of foam from the bags. Placement of a needle roller in the SpeedyPacker™ system allows for continual venting of the film used to create the bags; however, the current system is limited by its reliance on manual alteration of the system. In other words, with the needle roller in place, vents are always being made, with no variation in the pattern or number of vents created. Further, if it is necessary to create bags without ventilation, the bag-making apparatus must be shut down, the needle roller must be manually removed, and the apparatus must be restarted to begin producing more cushions. Further, vented bags cannot again be made without again shutting down the apparatus and manually replacing the needle roller. This presents a problem not only in that it is an inconvenience for the machine operator, but also in the lost production time and decreased efficiency associated with such necessary manual changes, and the inherent danger to the machine operator in having to continually remove and replace working pieces of the machinery.
Therefore, it would be advantageous to have a mechanism structured and arranged for attachment to a foam-in-bag cushion producing apparatus, such as the SpeedyPacker™, capable of creating perforations in the bag in an automated fashion, such that the mechanism can accommodate any type of bag, at any time, and in any combination. Such advantages are provided by the perforation forming mechanism of the present invention.